Method of forming a bright metallic deposit on the surface of objects



Aug. 8, 1944. M. TISCHER 2,355,186

METHOD OF FORMING BRIGHT METALLIC DEPOSITS ON THE SURFACE OF OBJECTSFiled DEC 27, 1937 Patented Aug. 8, 1944 UNITED STATES METHOD OF FORMINGA BRIGHT METALLIC DEPOSIT ON THE SURFACE OF OBJECTS Max Tischer, Bon U CLlpy, Czechoslovakia: vested in the-Alien Property Custodian ApplicationDecember 27, 1937, Serial No. 181,966 In Czechoslovakia December 29,1936 1 Claim.

In order to form a bright metallic deposit; on the surface of glass orother materials through chemical methods, use is made, in a knownmanner, of a solution of a metallic salt from which the metal isprecipitated in a finely divided state by the addition of a reducingsolution, so as to be deposited on the surface of the object to becovered with a bright metallic deposit. The two solutions, that is tosay the solution of metallic salt and the reducing solution, are keptseparate and they are mixed together only a short time before they areto be used, because reduction, and

consequently metal precipitation, take place im-' mediately after thismixing of the two solutions with each other. The objects on which abright metallic deposit is to be formed are immersed in the mixture ofthe solutions, or these objects are coated with this mixture ofsolutions or said mixture is atomized on the objects. In any case, it isclear that only a very small part of the metal present in the mixture ofthe solutions can be utilized for forming a. bright metallic deposit,because the precipitation of the metal starts as soon as the twosolutions have been mixed together and then it keeps going on in acontinuous manner, being distributed in a uniform fashion throughout themass of the mixed solutions, and only a small part of the metal thusprecipitated can deposit on the object, whereas the remainder depositson the'bottom or on the.

walls of vessel containing the mixture. When use is made of atomizingdevices, there is further produced, in the atomizing nozzles and in thefeed conduits leading to said nozzles, an immediate clogging resultingfrom the depositing of metal, which also takes place therein, so that.even after a short period of time it is necessary to proceed to acleaning by dissolution of the deposited metal by means of acid, whichis complicated and is a considerable delay to the operation.

The object of the present invention is to eliminate all these drawbacks,and also to obtain an improved adhesion of the bright metallic depositon its support, in such manner that the risk of scaling off, aphenomenon which is particularly frequent in the case of silver layers,is wholly eliminated.

The essential feature of the method according to the present inventionlies in the fact that the solution of metallic salt, necessary forproducing the bright metallic deposit on the objects, and the reducingsolution are atomized separately but simultaneously and are caused, inthis atomized state, to mix together and to act on the object to ordertofacilitate the reduction of the metal and I to obtain better adhesivequalities of the bright metallic deposit, the atomizing of thesolutions,

which are kept in distinct containers and are fed separately to theatomizing devices, is advantageously. effected by means of steam orheated gases.

According to another feature of the present invention, in order furtherto accelerate the separation of the metal from the atomized mixture andthe precipitation on the object to be coated with the bright metallicdeposit, and also in order further to improve the adhesive qualities ofthis deposit, it is advantageous to introduce steam or heated gases, inparticular gases having a reducing action, into the atomized mixturethat is produced.

In. order to carry out the method according to my invention, Ipreferably make use of an apparatus including two feed conduits, whichare located at a small distance from each other, correspondingrespectively to the solution of metallic salt and to the reducingsolution, these conduits leading to two atomizi ng nozzles arranged tomake an angle with each other. The atomizing nozzles are fed with steamor heated gases, preferably through a common conduit. The orifices ofthe feed conduits for the two respective solutions which serve toproduce the bright metallic deposit can be located so close to eachother that the simultaneous atomizing of these two solutions can beotbained by means of a single nozzle opening between said orifices andacting simultaneously on both of these solutions.

Other features of the presentinvention will result from the followingdetailed description of three specific embodiments thereof,

Preferred embodiments of the present invention will be hereinafterdescribed, with reference 40. to the accompanying drawing, given merelyby way of example, and in which:

Fig. 1 is a front elevational view of a first embodiment of theinvention;

Fig. 2 is a side elevational view corresponding 46 to Fig. 1;

Fig. 3 is a front elevational view of another embodiment of theinvention;

Fig. 4 is a side elevational view corresponding to Fig. 3.

Fig. 5 is a side elevational view of another embodiment of theinvention.

In the embodiment illustrated by Figs. 1 and 2 the apparatus includesfeed conduits I and I, located at a certain distance from each other andbe coated with the bright metallic deposit. In to supplying, one thesolution of the metallic salt,

and the other the reducing solution (these two solutions being preservedseparately) and a nozzle 4, 4' corresponding to each of these conduits.Steam or heated gas is fed to these nozzles through a common conduit 2,which is divided into two branches 3, 3', leading respectively to thelateral nozzles 4, 4' in question. These nozzles I, 4' are located at asmall distance from the respective outlets of conduits I, I, in suchmanner that the steam or hot gases issuing from these nozzles, whenflowing in front of these outlets of conduits l, I, suck out thesolutions respectively fed by these conduits and disperse them in theatomized state in the form of cones. As a consequence of the angle madeby the respective directions of nozzles 4, d, the two atomization conesintersect each other at a distance from the outlets depending upon thevalues of said angle, so that the atomized solutions are mixed together.I introduce, into this atomized mixture, the object on which a brightmetallic deposit is to be formed. The reduced metal is thus caused toprecipitate on this object, in the form of a highly adhesive brightmetallic deposit.

The apparatus is further provided with two lateral atomization nozzles5, 5', which are also arranged at an angle to each other and which arefed with steam or a heated gas through the common conduit 6. The conesof dispersion of these nozzles 5, 5' are directed toward the atomizedmixture in such manner that their jets mix with those of the coating(silvering) mixture, whereby precipitation of the metal on the object tobe coated (silvered) with this metal is accelerated and the adhesion ofthe deposit to the support is further improved. In particular, this isthe case when gases having a reducing action are fed through thesesupplementary nozzles sand 5'.

The embodiment illustrated by Figs. 3 and 4 corresponds to an analogousapparatus, in which, however, the two feed conduits l and I, throughwhich the metallic salt solution and the reducing solution,respectively, are fed, are arranged in such manner that their outletsare turned toward each other, at a small distance from each other. Tothese outlets corresponds a single atomizing nozzle 1, whichsimultaneously produces the atomizing of the two solutions and causesthem to mix together.

The additional atomization nozzles 5, 5', which are still arrangedlaterally with respect to the atomization cone thus produced, and whichare fed with steam or heated gas from conduit 8, serve, as in theapparatus above described, with reference to Figs. 1 and 2, toaccelerate the reduction and precipitation of the metal and to improvethe adhesive qualities of the bright metallic deposit.

Other change may be brought in the manner of using the above describedapparatus. For instance, the two feed conduits may be fed with the samemetallic salt solution in case the reducing agent is carried by thegaseous fluid atomizing jet.

As above described, one of the features of the invention resides .in thefact that the liquid solutions are atomized by means of jets of eithersteam or hot gases. It is obvious that the invention can be realized byatomizing by means of these jets a mixture of the two solutionscontaining the metallic salt and reducing agent.

The embodiment illustrated by Fig. 5 corresponds to an apparatus inwhich the metallic salt solution is fed through a feed conduit 9. To theoutlet of this conduit is connected another feed conduit I!) throughwhich is fed the reducing solution. l I is an atomization nozzle throughwhich steam or a hot gas, containing or not containing a reductingmedium, is fed to produce the atomization of the liquids onto thesurface of the object.

In a general mariner, while I have in the above description, disclosedwhat I deem to be practical and eflicient embodiments of the presentinvention, it should be well understood that I do not wish to be limitedthereto as there might be changes made in the arrangement, dispositionand form of the parts without departing from the principle of thepresent invention as comprehended within the scope of the appendedclaim.

What I claim is:

The method of forming a bright metallic deposit on the surface of anobject which comprises separately and simultaneously atomizing ametallic salt solution on the one hand and a corresponding reducingsolution on the other hand, simultaneously mixing these atomizedsolutions together and causing theatomized mixture thus formed to act onthe object to be coated with said metallic deposit, and introducing atleast one hot gas having a reducing action into the atomized mixturewhich is thus acting on the object MAX TISCHER.

